Patent GB-935037-A (GB)
Title: Improvements in or relating to power-assisted steering mechanisms, particularly for motor vehicles
IPC: B62D5/24
Filed: 1961-03-13
Abstract: 935,037. Steering vehicles. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. [March 13, 1961], [March 12, 1960], No. 9138/61. Class 79(5). A power assisted steering mechanism for a motor vehicle comprises a steering spindle, a steering nut co-operating with a steering worm rotatable by the spindle via a torsionally elastic element, an auxiliary power device acting upon a steering shaft to which movement of the steering nut is transmitted and being controlled by a valve comprising a bush movable in a housing by twist in the torsionally elastic element which extends through the steering worm and is connected at one end with the steering worm and is in engagement at this end with the control bush through a threaded stub internally of the bush or by means of an auxiliary bush, the end of the steering spindle being formed with bifurcations which engage in recesses in the control bush or auxiliary bush, the other end of the torsional element being connected with a part of the steering spindle which extends through a bore in , the steering worm. The steering spindle (not shown) is connected to a flange 22 rigid with a sleeve 17 in which a torsion bar 14 is secured by a pin 15, the other end of the bar 14 being secured by the location of shoulders 18 in complementary grooves in a steering worm 2, supported in the steering housing 5 by bearings 3 and 4, the bearing 3 being secured by a nut 7 and lock nut 10. The sleeve 17 is supported by a bearing 32 in the worm 2, and shoulders 25 and 26 in the worm are located within grooves 28 and 29, of sleeve 17, Fig. 3, whereby the degree of twist of the torsion element 14 is limited. The steering worm 2 co-operates with a nut 37 through a set of recirculating balls, the nut having a rack 39 engaging a toothed segment 41 integral with a steering shaft 40, to the free end of which a steering drop arm is connected. The steering shaft 40 is axially adjustable by a screw 64 and is provided with an arm 43 which engages through a roller 46 with a pair of power pistons 49 and 50 located within cylinders 52 and 53 and prevented from rotating by an angle piece 59. The space 67 between the pistons is. connected through a passage 68 with the reservoir of the hydraulic system. A bush 70 is axially displaceable in the valve casing 89 and in the worm 2 and is held against rotational movement relative to the shaft 17 by the engagement of bifurcated extensions of the latter in slots in the former (Fig. 6). A threaded extension 72 of the torsion bar 14 engages a corresponding thread in the bush 70 so that the relative rotational movement of the worm 2 to the steering shaft, as permitted by the clearance " s ", Fig. 3, causes axial movement of the bush which, at its outer end, is provided with fluid passages 'and cooperates with a stationary insert 81 and a housing 89 to provide a valve mechanism regulating the flow of liquid to one piston or the other, or to the reservoir, as appropriate, the valve housing and piston chamber being provided with a cover piece 56 which is provided with the various fluid passages 116, 121, 127 and 128 (Fig. 8) and a connection 120 to a pump. A spring 80 located between the member 81 and a shoulder in the bush 70 prevents axial play due to machining tolerances and the control edges in the valve members may be rounded (Fig. 5). The extent to which power assistance is provided may be determined by the rigidity of the torsion bar selected. The steering worm may have a left or right hand thread. In a modification, Fig. 9, wherein the pressure fluid is supplied by a pump 167 from a reservoir 169 and the valve housing 151 is attached to the outside of the steering housing, the fluid pressure is directed to one side or other of a double acting piston 176 attached in a conventional manner to the steering shaft. In a further embodiment, Fig. 10, the control valve is spaced apart from the axis of the worm and the spool 212 thereof is actuated through a lever 209, the pivot point 215 of which is adjustable by means of a screw 218.